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Giant Pumpkins Mean More Carbon Pulled from the Atmosphere

Chris Blunt tracks the distribution of biosolids by truck in monthly reports, helping the program ensure accuracy for regulatory reports and that vendors are paid the correct amounts.
  • Jacob Herson

It’s October, which means giant pumpkins are being grown at the Southeast Treatment Plant’s Demonstration Garden. No, these overgrown gourds aren’t haunted, they’re demonstrating the power of the San Francisco Public Utilities Commission (SFPUC) biosolids to turbo-charge plant growth. Bigger, faster-growing plants pull more carbon from the atmosphere, aiding the fight against climate change.

The Southeast Treatment Plant and Oceanside Treatment Plant produce approximately 59,000 tons of biosolids per year. Biosolids are biologically treated wastewater solids that are used as soil fertilizer on ranches in Northern California.

Farmers like biosolids because they make plants grow better and stronger, as demonstrated by these pumpkins. Plants pull carbon from the atmosphere in the process of photosynthesis, which turns sunlight, water, and CO2 into the energy they need to live, producing oxygen in the process. This carbon gets stored in the plant and when the plant dies and decomposes, or sheds leaves and roots, the carbon gets stored in the soil. Less carbon in the atmosphere and more in plants and soils helps reduce the effects of climate change.

Soils are also healthier when they have more carbon, leading in turn to stronger-growing plants. Biosolids are 25% carbon, which is how they make soils healthier and make plants grow better. Soils have lost much of their carbon due to land use changes like deforestation. Biosolids can help repair that damage.

Each year, SFPUC biosolids applied to Northern California ranches avoid 4,000 metric tons of carbon emissions, storing that carbon in plants and soils instead (calculated using the EPA greenhouse gas equivalencies calculator). That’s an amount of avoided emissions equivalent to:

  • 890 gasoline-powered passenger vehicles driven for one year.
  • 10.3 million miles driven by an average gasoline-powered passenger vehicle.
  • 778 homes’ electricity use for one year.

Benefiting farmers, plants, soils, and the planet, the SFPUC biosolids program is such a good idea – it’s scary!